what is the fovea? the small depression at center of macula with the ___
highest spatial acuity
what enters and leaves the optic disk?
blood vessels enter and retinal axons leave the eye
: ant. ciliary and long post. ciliary arteries supply blood to the
iris and ciliary body
Uveal tract consists of three structures:
choroid, the ciliary body and the iris.
Delivery of metabolic substrates and oxygen to the retina is accomplished by (2)
the inner retinal and choroidal.
what is the posteriro chamber
Region between the vitreous and the lens.
what produces aqueous humor?
the vascular component of the ciliary body.
where is the vitreous humor
the space between the back of the lens and the surface of the retina.
what pigment does the macula contain?
a yellowish pigment (xantophyl). Supports high acuity.
The ocular vessels are derived from the
all from the ophthalmic artery (OA),
what are the two distinct vasciualr systems that supply the eye
a) the anterior segment (iris and ciliary body)
b) the retinal systems.
Focusing Power of a lens =
Curvature of surface + differences in Refractive Indexes
focal length - how strongly a lens ___
Greater lens curvature = Greater converging power = __ focal length
diopters - measure of
emmetropic eye - is
elaxed, unaccommodated, focused on object at “infinity”
what is responsible for most of the refraction in the eye
Cornea - 80%
lens does 20%
Refractive index of cornea =
accommodation - the___ to focus on near objects
curvature of the lens increases
what muscles contract to increase the curvature of the lens? which relax?
ciliary muscles contract, zonule fibers relax
when the curvature of the lens increases the focal length
Accommodative triad/near reflex:
eye accomm. + pupil constriction + eye convergence
eye accomm. + pupil constriction is mediated by the
parasymp. nerves from Edwin Westphal nucleus of pretectum
The ___ lens is transparent, has crystallins, with high refractive index of 1.42,
• cataract - disorder of___ that destroys lens transparency,
lens cell fibers or aggregation of crystallin
___ is the leading cause of blindness worldwide.
risk factors for cataracts
aging, diabetes, sunlight, smoking
sx of cataracts
hazy vision, poor night vision, glare, faded colors
tx of cataracts includes
surgical replacement with an artificial lens